U.S. Pat. No. 5,226,077, issued Jul. 6, 1993, describes a headset amplifier with automatic log-on and log-off detection. The disclosure in U.S. Pat. No. 5,226,077 ('077 Patent) is incorporated herein by reference.
As described in the '077 Patent, a number of manufacturers have developed sophisticated telephone switching networks called "automatic call distribution" systems or ACDs. These systems are used in call centers such as for airline reservations, banks, telemarketing, etc., for receiving a large number of calls from the outside and distributing them to various operators at the call center. The operators in call centers typically use telephone headsets that are connected to the ACD through an amplifier module. In many current headset systems, the amplifier is detachably connected to either the ACD or to a telephone set which is, in turn, connected to the ACD. The headset is detachably connected to the amplifier via a wire that includes a "quick disconnect" element. When the operator goes on a break, she will use the quick disconnect to separate the headset from the amplifier, allowing her to walk away from the station while continuing to wear the headset. Headsets are typically not shared among operators for sanitary reasons.
Some of the more sophisticated ACD/telephone systems include a mechanism for detecting when the amplifier has been disconnected from the system. The detection system permits the ACD to determine whether the operator is available to take a call. Unfortunately, currently designed detection circuits are unable to determine when the operator has unplugged the headset from the amplifier and left the station.
This problem was overcome by the invention described in the aforementioned '077 Patent. The '077 Patent described a system wherein the amplifier was capable of monitoring when the headset became disconnected from the amplifier. Upon detection of that disconnection, the amplifier functioned to "emulate" the disconnection of the amplifier from the telephone switch, even though the amplifier remained connected. This emulation function allows the ACD to determine when the headset had been disconnected from the amplifier and the operator was unavailable.
Further refinements of this system are disclosed in U.S. patent application Ser. No. 08/469,481 ('481 Application), filed Jun. 6, 1995, also incorporated by reference. This disclosure describes an approach which is desirable where wireless headsets are used. In a wireless headset, there is no hardwire connection between the amplifier and the headset. As long as the headset remains within range of the amplifier base, communications can proceed. If, however, the operator moves beyond the range of transmission, the call cannot be continued. In accordance with the '481 Application, the amplifier is provided with a circuit for determining when the headset has gone out of range. When the headset goes out of range, the amplifier functions to emulate the disconnection of the amplifier from the switch even though the amplifier remains connected.
The emulation function used by the amplifier is based upon the protocol which is being monitored by the ACD. For example, the ACD can be designed to look for a change in either the current or resistance at the amplifier connection. These emulation functions are performed for both the hardwired or wireless embodiments.
There are a number of existing telephone switches (ACDs) which are not provided with automatic log-off sensing features. Amplifiers capable of emulating the disconnection of the amplifier from the switch are therefore not useful in these systems since the switch does not provide any means for detecting that disconnection. For many manufacturers, the cost for redesigning switches and telephones to provide this detection capability is not feasible. The object of the subject invention is to provide a novel approach for signalling the availability of the operator in systems which do not have any detection capability designed into the telephone or the switch.